Sri-Lanka is becoming a major spot for whales and dolphins watching in the world. Specially Dontra Point of down south is the main port of Sri-Lanka during month of December to April (Peak sighting months are December, January and April). During these month more than 95% chances of spotting Sperm Whales and Blue Whales as their migration path just off from Dondra Point. Also there are good chances to witness the Spinner Dolphins too.
I am able to arrange whales watching trips from Mirissa in fully insured trawler boat which has toilet facilities to cater to the long duration. Usually tour will star at 6.a.m. and the duration of sailing is 3-5 hours at sea. I will provide free breakfast, life guards, and life jackets as well. Mirissa is 2 hours drive from Colombo. You can use Southern Express way to reach to Mirssa easily.
Kalpitiya is famous beach area because of highest densities of Dolphins in Sri-Lanka during November to March. At the time you can witness 1000-1500 dolphins. I can arrange you accommodation and boats according to your purpose. Kalpitiya is 4 hours drive from Colombo. You can use Colombo-Katunayake express way to reach to Kalpitiya easily.
Whales and dolphins watching also possible during June to September in the eastern part of the country such as Trincomalee.